The spinal cord is very sensitive to any compressive forces. If there is any pressure on the nerves it will generally result in pain, weakness, or numbness. Residual pain after surgery is usually due to residual nerve compression. This is due to many sources but the most common are: reherniation of the disc, Incomplete decompression of the spinal cord or the foraminal canals. Numbness or weakness that results after a surgery may signify nerve damage that may be non-repairable. Pain is usually due to continued forces acting on the spinal cord or the nerves themselves. These forces may be stretching or compressive, although compressive is more common. Many people get pain a few months after their surgery and they are told that it is due to scar tissue or arachnoiditis. This is usually only partly true. The scar tissue in and of itself isn't the problem. The problem is that the scar tissue is acting as a space occupying lesion and thus it is compressing the nerves against a solid object such as bone or disc. Another important reason for residual pain after surgery is that the surgery was performed at the wrong spot. As stated before the spinal cord is very sensitive to any compression and if the surgery was done in the wrong area then residual pain may be present. This is not to say that the surgery performed a incorrect surgery, nerves can be compressed at various areas and most surgeons partially guess at where the nerve is being compressed. This is one reason why if we have any question as to what your source of pain is we will perform diagnostic blocks to confirm our diagnosis. The correct diagnosis will usually lead to the correct surgery and thus resolution of the pain. Finally, another reason for residual pain is that the original pain was resolved but a "new" pain has developed. People often focus on their "worst" pain and once that "worst" pain is resolved, then "new" pains may come to the surface. The best way to describe this is if someone hit your thumb with a hammer, until the thumb pain resolved, you wouldn't be focusing on your back pain. Our mind focuses on the most important insulting injur